Receptor-type tyrosine kinase HER2 protein (Human EGF receptor-2: Akiyama et al, Science Vol. 232, Page 1644-1646, 1986) is found to have existed in normal tissue at the stage of initial development. However, it is found not to exist in normal adult tissue; it mainly exists only in cancer cells. For this reason, an antibody capable of recognizing homo- or hetero-dimer or homo-polymer HER2 protein is used for the treatment of high-level HER2 protein-expressing cancer for the purpose of inhibiting the proliferation of corresponding cells. Hence, HER2 antibody Herceptin ((Trademark) general term: trastuzumab) is widely used in high-level HER2-expressing breast cancer treatment.
A receptor-type tyrosine kinase HER2 protein inhibiting antibody lays question of its probability in oral absorptivity, administration style and elicitation of heart failure or allergy. On this account, a highly reliable inhibitor with the capability of oral administration and repetitive administration, which can selectively suppress the proliferation of HER2-expressing cancer cells, is strongly required.